Substances identified as Toxic Air Contaminants by
the Air Resources Board, pursuant to the provisions of AB 1807** and AB 2728** (includes
all Hazardous Air Pollutants listed in the Federal Clean Air Act Amendments
of 1990).

Information within the square brackets refers to the corresponding subcategory on the Substances By Category version
of the list. Click on a subcategory to go it.

Substances NOT identified as Toxic Air Contaminants,
known to be emitted from stationary source facilities,
which are being evaluated for entry into Category I. Factors considered in this evaluation include carcinogenic
and noncarcinogenic health effects, emissions and exposure in California.

Substances which have already been identified by the Air Resources Board
as Toxic Air Contaminants through a
comprehensive AB 1807 risk assessment and which have health values developed by the Office of Environmental
Health Hazard Assessment and approved by the Scientific Review Panel. A full risk assessment report is available

To be listed as a Toxic Air Contaminant, these substances will go though
a comprehensive AB 1807
risk assessment.

0

These substances have been nominated for the development of additional health
values.

+

These substances are active ingredients in pesticides in California. For
further information regarding the
pesticidal uses of these compounds, please contact the Department of Pesticide Regulation.

Note 4:

For all listings above which contain the word "compounds" and
for glycol ethers, the following applies:
Unless otherwise specified, these listings are defined as including any unique chemical substance
that contains the named chemical (i.e, antimony, arsenic, etc.) as part of that chemicalís infrastructure.

Note 5:

Chlorinated Dibenzo-P-Dioxins and Dibenzofurans:
The cancer potency value for
2,3,7,8-tetrachlorodibenzo-p-dioxin
was determined for the identification of chlorinated dioxins and
dibenzofurans as toxic air contaminants in 1986. At that time, the Board identified dibenzo-p-dioxins
and dibenzofurans chlorinated in the 2,3,7, and 8 positions and containing 4,5,6, or 7 chlorine atoms as
toxic air contaminants. Since 1986, International Toxicity Equivalency Factors (ITEFs) have been developed
which are used to evaluate the cancer risk due to exposure to samples containing mixtures of chlorinated
dibenzo-p-dioxins
and dibenzofurans. ITEFs are numerical factors that express the toxicity of an individual
chlorinated dibenzo-p-dioxin
or dibenzofuran relative to the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin.
ITEFs are listed for 16 chlorinated dibenzo-p-dioxins and dibenzofurans.

Note 6:

Diethanolamine: There
is a 1997 draft report by the National Toxicology Program that shows evidence of
carcinogenic activity in mice. (This may result in a change of the cancer classification.)

Inorganic Lead: Due
to information on non-cancer health effects showing no identified threshold, no
Reference Exposure Level has been developed. However, guidelines for assessing noncancer health
impacts are currently being developed by ARB staff.

Note 9:

Polycyclic Organic Matter:
Includes organic compounds with more than one benzene ring, and which
have a boiling point greater than or equal to 100 oC.

Note 10:

Benzo[a]pyrene: Potency
Equivalency Factors (PEF) have been developed for 24 polycyclic aromatic
hydrocarbons (PAHs). Using benzo[a]pyrene as a reference compound, a weighting scheme for PAHs
was developed in the 1994 Air Resources Board document entitled, Benzo[a]pyrene
as a Toxic Air
Contaminant. When a specific potency value is developed for a
chemical, it should be used in place
of the PEF.

Note 11:

Cyanide Compounds:
X'CN where X=H' or any other group where a formal dissociation may occur.
For example, KCN or Ca(CN)2

Note 12:

Radionuclides: A type of atom which spontaneously undergoes radioactive
decay.

Environmental Tobacco Smoke:
An AB 1807-type of health assessment for Environmental Tobacco Smoke
was conducted by the Office of Environmental Health Hazard Assessment (OEHHA) and was approved by
the Scientific Review Panel on June 19, 1997. The Air Resources Board accepted the report from OEHHA
on October 23, 1997 and subsequently forwarded to the Department of Health Servicesí Tobacco Control
Program for appropriate action.